Description
Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.
Affected products
haxx: curl
References5
- curl.se/docs/CVE-2026-6276.html PatchVendor Advisory
- hackerone.com/reports/3671818 ExploitIssue TrackingThird Party Advisory
- hackerone.com/reports/3671818 ExploitIssue TrackingThird Party Advisory
- curl.se/docs/CVE-2026-6276.json Product
- www.openwall.com/lists/oss-security/2026/04/29/13 Mailing ListThird Party Advisory
Metrics
- CVSS 3.1
-
7.5
HIGH
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS — exploit probability
- 0% percentile: 22 · as of 14 November 2026
- CWE
- CWE-346CWE-319
Could this be exploited in your environment?
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